PROJECT SUMMARY The objective of this proposal is a small (ink pen-sized) tool that non-invasively measures dental pocket depths and assesses gingival health using ultrasound. We are motivated by studies showing that dental pain dramatically decreases quality of life but that nearly 50% of Americans have some form of periodontitis. Our scientific premise is that the current approach to measuring pocket depths is painful and imprecise with coefficients of variation as high as 40%. This results in poor patient compliance and poor diagnostic insight ultimately leading to attachment loss. Therefore, less painful and more accurate diagnostic tools could improve dental health and thus overall quality of life. Our preliminary data (J. Dent. Res., 2017) used an oral rinse based on the melanin nanoparticles from food-grade squid ink to map and measure the contours of the entire periodontal pocket in swine models with novel photoacoustic imaging. We noted good correlation of these image-based measurements to non-blinded conventional probe depth measurements via Bland- Altman analysis. However, the current transducer is ~20 cm by 5 cm and can only access the incisors in humans. The goal of this research is to build a smaller prototype suitable for intraoral ultrasound imaging. The aims below describe how we will build and validate this device. Aim 1 will build the device. We will combine a single element transducer and light emitting diodes into a compact pen-like design. This will use the expertise of Dr. Jokerst in acoustics and Dr. Hall in electrical engineering. Aim 2 will characterize the performance of the device using standard reference materials (imaging phantoms). We will measure the light homogeneity, axial resolution, lateral resolution, depth of penetration, frame rate, and scan time. Aim 3 will validate the ability of this device to measure the pocket depths in an ex vivo swine model. We will irrigate the pockets with a food-grade contrast agent (squid ink melanin nanoparticles) and image the pocket and surrounding gingiva. We will compare the values created by imaging to the gold-standard probe depths collected by Dr. Koka. We will evaluate the imaging data for bias and reproducibility with both methods, and we hypothesize that depths from imaging will correlate to blinded conventional periodontal probe data (R2>0.90). This work is innovative because it will quickly (2 minutes) and non-invasively map the contours of the entire dental pocket with low variance. Our preliminary data and the expertise of the research team in engineering, imaging, and periodontology underscore the feasibility of these ideas. The clinical impact will be a more reliable and less invasive tool to monitor attachment loss?this will increase patient compliance and facilitate more comprehensive estimates of attachment loss to ultimately decrease periodontitis rates. Long-term, this oral imaging tool would have many other applications in characterizing oral soft tissue including peri-implantitis and aberrant biofilms.